The invention is generally directed to a method and apparatus for the promotion of wound healing. More particularly, the present invention relates to providing fluid irrigation and vacuum drainage of a wound.
Negative pressure wound therapy, also known as vacuum drainage or closed-suction drainage is known. A vacuum source is connected to a semi-occluded or occluded wound dressing. Various porous dressings comprising gauze, felts, foams, beads and/or fibers can be used in conjunction with an occlusive semi-permeable cover and a controlled vacuum source.
In addition to using negative pressure wound therapy, many devices employ concomitant wound irrigation. For example, a known wound healing apparatus includes a porous dressing made of polyurethane foam placed adjacent a wound and covered by a semi-permeable and flexible plastic sheet. The dressing further includes fluid supply and fluid drainage connections in communication with the cavity formed by the cover and foam. The fluid supply is connected to a fluid source that can include an aqueous topical antibiotic solution or isotonic saline for use in providing therapy to the wound. The fluid drainage can be connected to a vacuum source where fluid can be removed from the cavity and subatmospheric pressures can be maintained inside the cavity. The wound irrigation apparatus, although able to provide efficacious therapy, is somewhat cumbersome, difficult to use, and generally impractical. Such a device does not address various factors concerning patients, specifically ease of use, portability and the ability to provide therapy with a minimum amount of unwanted mechanical noise.
Other devices use vacuum sealing of wound dressings consisting of polyvinyl alcohol foam cut to size and stapled to the margins of the wound. The dressings are covered by a semi-permeable membrane while suction and fluid connections are provided by small plastic tubes introduced subcutaneously into the cavity formed by the foam and cover. Such devices alternate in time between vacuum drainage and the introduction of aqueous medicaments to the wound site. Such devices also fail to address portability, ease of use and noise reduction.
Therapeutic negative pressure wound healing devices or vacuum assisted continuous wound irrigation devices require a control mechanism to maintain vacuum at a desired predetermined level. Typically, these control systems rely on a (negative) pressure sensor of some type that converts the measured pressure to an electrical signal that can be utilized by control circuits to maintain a preset level. Many sensors use an electrical strain-gauge technology that produces a voltage signal in proportion to applied vacuum. Other sensors are electromechanical in nature and produce a changing resistance in proportion to applied vacuum. Still other sensors are mechanical switches that are off when vacuum is above a predetermined level, and on when vacuum is below a predetermined level. In any case, in order to efficiently maintain the vacuum of a suction wound therapy device, some type of electrical or mechanical sensor is necessary as part of a control loop.
The cost of the pressure sensor can be a significant percentage of the overall cost of the product. While these sensors are readily available and well known, they are also relatively expensive. Typically electronic sensors such as the Motorola MPX5050 cost approximately $15 in single piece quantities. Similarly, purely mechanical pressure switches, such as those available from AirLogic, cost between $18 and $25 in single piece quantities.